In manufacturing a general semiconductor integrated circuit, an integrated circuit having a fine pattern is formed by repeatedly performing various processes such as exposure, deposition process, etching process and heat treatment on the substrate such as a semiconductor wafer.
Thus various processes are performed by using a substrate processing apparatus having a processing chamber configured of exclusive instruments for performing respective processes. The substrate processing apparatus is composed by connecting one or several various processing chambers to a transport chamber for storing a conveyance robot. The conveyance robot is provide with a conveyance arm for mounting and transporting the disc-shaped substrate such as a semiconductor wafer at the center. Further, the transport chamber and the processing chambers are provided with means for maintaining each inner part in a vacuum environment, and connected to each other through gate valves. Here, the disc-shaped substrate held by the conveyance robot is transported, mounted on a mounting table installed to the processing chamber by using the conveyance arm, and then, the various processes are performed on the disk-shaped substrate.
The substrate processing apparatus is required to precisely transport the substrate at a predetermined position of the mounting table in order to appropriately process the disc-shaped substrate mounted on the mounting table. Therefore, the substrate processing apparatus needs the disc-shaped substrate precisely positioned on the predetermined position of the mounting table in the processing chamber. After first detecting positional misalignment of the objective disc-shaped substrate, if a positional misalignment occurs, the disk-shaped substrate needs to be located on the predetermined position by correcting the positional misalignment. Specially, it is difficult to directly detect the position of the disc-shaped substrate in the processing chamber because of processes executed or substance used/deposited in the processes. Therefore, it is necessary to detect the position of the disc-shaped substrate in the predetermined place within the transport chamber which is connected with the processing chamber.
In a conventional method for detecting position of the disc-shaped substrate, for example, like in patent literature 1, the disc-shaped substrate is mounted on a rotatable pedestal, the periphery is detected by a line sensor as being rotated, and the positional misalignment is detected based on a rotation angle of the pedestal and detection results from the line sensor.
However, the rotatable pedestal and the line sensor must be installed into the transport chamber with the method disclosed in Patent literature 1, and therefore, this requires increasing the size of the transport chamber. Further, the disc-shaped substrate held by the conveyance robot requires a series of actions for detecting the positional misalignment by being once mounted on the pedestal and rotated, therefore causing the problem that throughput is reduced.
Accordingly, recently, as disclosed in Patent literature 2, the peripheral part of the semiconductor wafer has been captured for a plurality of times, and the position of the semiconductor wafer has been detected based on the captured images. That is, a plurality of cameras are located on the upper surface outside the transport chamber and a light source is located on the undersurface outside the transport chamber opposing the cameras. The cameras are positioned so as to pick up images of the peripheral part of the semiconductor wafer being transported in the transport chamber, and capture the peripheral part in passing timing of the semiconductor wafer. Here, the position is detected based on image data capturing a plurality of peripheral parts.